10 BULLETIN 904, U. S. DEPARTMENT OF AGRICULTURE. 
on germs from the dry process and below 8 per cent when using 
material from the wet process. 
A peculiar series of explosions often takes place in these expellers, 
mostly when used on germs obtained by the dry process. The cause 
does not appear to be well understood, but it is the general opinion 
that an excessive or an insufficient amount of either moisture or 
fiber is responsible. 
The oil obtained, which in most cases is of a golden color, is next 
passed through filter presses which remove the fine meal. This 
Fic. 9.—Complete 1-expeller oil plant. 
meal is then returned to the expellers and mixed with the fresh 
material. See: 
Hydraulic presses are used only to a very limited extent, having 
been almost entirely displaced by expellers. The question of the 
relative expense of operating presses and expellers is interesting, and 
several factors are involved. The cost of operating presses is some- 
what increased at present (1920) owing to the expense of the press 
cloths, which cost about $2 a yard. It is estimated that the entire 
set of cloths must be replaced every 60 days, and since 45 yards are 
required for one press of 15 plates, this item amounts to $90, or $1.50 
ee eT 
